Acoustical apparatus



J. PRESTON 3 ACOUSTIGAL APPARATUS March 11, 1941.

Filed May 29, 1937 Erwentor Patented Mar. 11, 1941 UNITED STATES PATENTOFFICE ACOUSTICAL APPARATUS ware Application May 29, 1937, Serial No.145,467

4 Claims.

This invention relates to acoustical apparatus, and more particularly toacoustical diaphragms and mountings therefor.

The advantages of a direct acting diaphragm have been long recognized,as has also the desirability of having such diaphragms act as nearlylike a true piston as possible. Because of its lightness and almostideal piston-like action, aluminLun has been rather extensively used fordirect acting cones. In such cones or diaphragms, the peripheralportions have been bent back to provide a suitable mounting ring for thediaphragm. The chief objection to the use of aluminum cones of thistype, where the displacement of the cone exceeds that of a few mils, isthe breakdown of the peripheral suspension because of the relatively lowelastic limit of aluminum.

The primary object of my present invention is to provide an improvedmounting for aluminum and other similar diaphragrns which will be freefrom the defect heretofore noted.

More specifically, it is an object of my invention to provide animproved mounting for aluminum cones so that the cones may be displaceda distance greater than the elastic limit thereof would permit under theconditions of use of prior art aluminum cones.

Anotherobject of my invention is to provide an improved diaphragmsuspension as aforesaid which is inexpensive of manufacture and highlyefiicient in use.

A further object of my invention is to provide, in electro-acousticalapparatus which includes a diaphragm, an improved suspension member forsaid diaphragm which will avoid the necessity of additional centeringmeans for the diaphragm with respect to the magnetic structureassociated therewith.

In accordance with my present invention, I make the mounting ring of amaterial which is stiff in its own plane but which is flexible in aplane at right angles to its own plane, the material preferably havingan elastic limit greater than that of aluminum. When such a mounting isused, the danger of breaking down is eliminated and the life of the coneis greatly increased.

The novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation,together with additional objects and advantages thereof, will best beunderstood from the following description of a specific embodimentthereof when read in connection with the accompanying drawing, in whichthe single figure is a cross-sectional view of a so-called conicaldiaphragm and mounting therefor.

Referring more specifically to the drawing, I have shown a cone ordiaphragm I provided with a voice coil form 3 on which a voice coil 5 iswound, the cone I being so mounted with respect to the pole pieces I and9 of a suitable magnetic structure that the voice coil 5 is disposedwithin the air gap II.

For mounting the cone or diaphragm l on a suitable supporting member(not shown) I employ a mounting ring [3 of a material which is stiff inits own plane but which is flexible enough to permit movement of thecone l in a plane at right angles to its own plane. The ring 13 may becemented It!) the peripheral flange 2 of the diaphragm I, or securedthereto in any other suitable manner. Among the materials which I havefound suitable for this purpose are phosphor bronze, steel, and fiber.These materials are all tough and capable of withstanding repeatedstresses at high frequencies without breaking down, as would aluminum.Moreover, the use of i any of these materials insures proper centeringof the voice coil 5 in the air gap ll without the necessity of providingany additional centering means such as the spiders conventionally foundin most loud speakers and made necessary when using mounting rings ofleather, felt, rubber, rubberized fiber or the like known in the priorart, and all of which fail to have the necessary stiffness in the planeof the suspension ring.

From the foregoing description, it will be obvious that I have providedan improved suspension for diaphragms which is free from thedisadvantages present in prior art mountings. Although I have shown anddescribed but one specific embodiment of my invention, I am fully awarethat many other modifications thereof are possible, and I thereforedesire that my invention shall not be limited except insofar as is madenecessary by the prior art and by the spirit of the appended claims.

I claim:

1. In electroacoustical apparatus, the combination of means providing amagnetic field and including an air gap, a diaphragm having a voice coilform located in said air gap, and an annular mounting member for saiddiaphragm secured to the peripheral portion thereof, said mountingmember being stiff in its own plane and relatively flexible in a planenormal to its own plane and being of a material which has an elasticlimit greater than that of the material of said diaphragm, and saidmounting member constitutin the sole means for supporting said diaphragmand for retaining said voice coil form in said air gap in predeterminedrelation thereto.

2. The invention set forth in claim 1 characterized in that saidmounting member is made of fiber.

3. The invention set forth in claim 1 characterized in that saidmounting member is made 10 of phosphor bronze.

4. In acoustical apparatus, the combination of a vibratable diaphragmmade of aluminum and a substantially plane mounting member thereforattached to the peripheral portion of said diaphragm, said mountingmember being stiff in its own plane but flexible in a plane normal toits own plane, and being of a material which has an elastic limitgreater than that of aluminum.

